Buying a van equipped with a wheelchair lift can be a problem due to the considerable cost of a van and the lift. As a result, some people use ramps in order to maneuver a wheelchair into a van without a wheelchair lift. Crump, U.S. Pat. No. 4,912,796, issued Apr. 3, 1990, and incorporated herein by reference, discloses an example of such a ramp.
Unfortunately, it is all too easy to accidentally bump one's head as one is entering or leaving a van. The user either has to purchase a van with a raised door, which is often very expensive, or has to duck or otherwise squat down in the wheelchair when entering the van.
In addition, there may be situations where a wheelchair user wishes to alter the height of the chair seat. Tables are provided at various heights, from coffee table height to bar height, and a wheelchair user often finds themselves at the wrong height for a given table.
Vans equipped with handicapped controls can be very expensive to build, as often the floor of the van needs to be made adjustable in order that the wheelchair user is at the right height with respect to the vehicle controls. Hydraulically lowering floors and the like can be quite expensive in addition to hand controls, which are relatively inexpensive. If a wheelchair user could have an adjustable height wheelchair, the cost of converting a van to wheelchair use could be decreased significantly. Given that such an adjustable height wheelchair would allow the use of inexpensive ramps in place of complicated, bulky, and difficult to use lifts, handicapped accessible and operable vans could be made more affordable, and thus more accessible for wheelchair users.
Of course, traditional office chairs and the like are known to use pneumatic cylinders that are pre-charged and sealed like a pneumatic spring. By releasing a lever, the user can push themselves up or down to a desired chair height.
For a wheelchair user, however, such a solution may not be workable. To begin with, the traditional pneumatic spring of an office chair serves only to reduce the force required to raise or lower the chair. The pneumatic spring does not actually raise or lower the user in most instances. Rather, the user raises or lowers the chair by altering their weight on the chair, which requires the use of their legs. For most wheelchair users, this may be a problem.
In addition, most office chairs use a centrally located pneumatic cylinder that acts as a support for the chair. Such a central cylinder may be useful in that it allows the chair to swivel. However, for a wheelchair, such a design may not be suitable, as it may not provide the stability needed for the seating surface.
Mechanical mechanisms are known in the art for raising and lowering wheelchair seat heights. Bergstrom, et al., U.S. Pat. No. 5,520,403, issued May 28, 1996, and incorporated herein by reference, discloses a wheelchair with translating seat and patient lift. While Bergstrom discloses an adjustable seat, note that the seat is designed to be adjusted with a hand crank, used from behind the seat. Thus, a second person is needed to raise and lower the wheelchair user, and the wheelchair user cannot raise and lower themselves. Moving the crank to a position where the wheelchair user can reach it may not be an option, as the crank would either be in the way, or in an awkward position for cranking. In addition, the user may have some other disability that would prevent them from turning such cranks.
One solution would be to provide a wheelchair with an electrical mechanism to raise and lower the seating surface. Shaffer, U.S. Pat. No. 4,231,614, issued Nov. 4, 1980, and Weant et al., U.S. Pat. No. 3,807,795, issued Apr. 30, 1974, both of which are incorporated herein by reference, disclose electromechanical devices for altering the position of a wheelchair user. While both of these devices may perform their intended function, the weight, complexity, and cost of batteries may make them impractical and too expensive for regular use. A wheelchair should be as light and as inexpensive as possible such that it is easy to roll, and easy to afford for the user.
Finch et al. U.S. Pat. No. 5,772,237, issued Jun. 30, 1998, discloses a suspension for a powered wheelchair using fluid cylinders. Finch explicitly states that his suspension can be lowered to assist in getting in and out of a van, and thus does address one of the problems outlined above. However, Finch uses an expensive and complex suspension system using multiple cylinders and an adjustable suspension in connection with a powered wheelchair. This system might not be adaptable to a manually operated wheelchair, for example.
Thus, it remains a requirement in the art for a wheelchair with an inexpensive, lightweight, and affordable height adjustment feature.